Formatted Title

Sources of TCE in Indoor Air: An Update on U.S. EPA and State Policies and Regulations

Background/Objectives

Indoor and ambient sources of VOCs can be important confounders in evaluation of vapor intrusion.  The detection of a VOC in an indoor air sample above a regulatory screening level is typically not sufficient to demonstrate vapor intrusion.  Rather, multiple lines of evidence are usually required to identify the VOC source.  Identification of trichloroethylene (TCE) sources can be a particular challenge because of the very low regulatory screening levels (sometimes less than 1 µg/m³) and the diversity of industrial and consumer products that have historically contained TCE.  Understanding the current and evolving uses of TCE in industrial applications and consumer products is important for accurate assessment of TCE vapor intrusion.

Approach/Activities

The regulatory risk evaluation of TCE has evolved over time. Since the early 2000s, the regulatory exposure thresholds deemed protective against cancer and non-cancer health effects have decreased.  As a result, either short-term or long-term exposure to TCE at concentrations as low as single digit µg/m³ concentrations is considered to be a potential concern.  In turn, this has led to gradually increasing restrictions on the use of TCE in a wide variety of consumer products and industrial applications.

Results/Lessons Learned

Historically, TCE has been used for degreasing and other industrial applications.  TCE has also been used in automotive parts cleaners, carpet and other cleaners, shoe polish, glues, gun cleaner, pepper spray and a wide range of other consumer products.  The use of TCE in consumer and industrial products has decreased over time as a result of increased regulation and increased manufacturer awareness of health concerns.  Recent regulatory developments include:

• Since 2002, California has banned the use of TCE (and PCE and methylene chloride) in a wide range of consumer products.
• In 2022, Minnesota banned most uses of TCE (including degreasing) at industrial facilities that require air permits.
• In December 2022, the USEPA finalized a regulatory finding of “unreasonable risk” for most uses of TCE in industrial processes and consumer products. 
• In October 2023, the USEPA published draft rules that would ban TCE from essentially all commercial and consumer products and prohibit many industrial uses of TCE and greatly restrict the remaining uses.

While these developments have greatly reduced the use of TCE in consumer products and industrial applications, indoor sources of TCE have not been eliminated.  We recently identified “Food Grade Silicone Lubricant” as the source of TCE detected in indoor air during a vapor intrusion investigation at a warehouse building.  During a change in vendors in the summer of 2023, the building tenant had inadvertently switched from a lubricant without TCE to a nearly identical product from the same manufacturer that contained 25% to 50% TCE. 

If the draft USEPA rules are adopted, the remaining TCE-containing commercial and consumer products will be removed from the market within one year.  After this time, indoor sources of TCE are less likely to confound vapor intrusion investigations.  However, some older TCE-containing products may still be present in commercial and residential spaces.  For some period of time, future vapor intrusion investigations will still need to account for this possibility.